There is definitely a seasonality to human births, writes Beth Skwarecki at Double X Science. The complicated bit is that human baby season isn't necessarily the same (or as strongly expressed) from place to place and culture to culture. In the United States, significantly more babies are born in July, August, and September. Meanwhile, in Europe, babies seem to make their way into the world in spring. So there's clearly a cultural component to this — but culture doesn't explain it, entirely. Skwarecki's piece explores a messy place where culture, genetics, and circadian rhythms intersect.

USDA scientist Lewis Ziska, among other researchers, has found that ragweed is one of the plants whose growth is most enhanced by exposure to higher concentrations of carbon dioxide. Not only does the ragweed grow faster when exposed to more CO2, it also produces more pollen. This is especially an issue in cities, which have higher concentrations of CO2 than rural areas, thanks to having a higher concentration of cars and other CO2 emitting sources. Extra bonus: There's also some evidence that allergy seasons are getting longer, as Spring starts earlier and Winter takes longer to truly set in.